When pipe diameters are small and distances short, it is possible to use soil-displacing methods in which the pipe is thrust into the desired direction by applying a sufficient force. A shaped head mounted at the end of the pipe displaces as much soil as is required by the cross section of the pipe. Such a device was presented in publications DE-1811421 and FI 51726. According to these methods the soil is forced to pack sideways and later soil is packed more when enlarging the hole or when soil is removed through the hole. The hole can be enlarged if it remains open without collapsing.
Swedish publication 446472 discloses a method of forcing cylindrical parts into ground by adding extra parts successively in starting excavation. The cylindrical parts are filled by soil which is removed by some known methods when the cylinders are in the built tunnel.
Methods which need an arbor to make the hole or to enlarge the hole have a disadvantage that holes can easily collapse. For this method is advantageous that the arbor pull a cable when, for example, it is forced under the road.
In the method according to Swedish publication 446 472 the diameter of pipe is so large (2 m) that the pipe must be emptied of soil by soil transporting apparatus. A pipe with a large diameter cannot be pushed under roads or railways without road damaging movements and displacements.